Problem: The angles of a pentagon are in arithmetic progression. One of the angles, in degrees, must be:
Answer Choices:
A. 108108108
B. 909090
C. 727272
D. 545454
E. 363636 Solution:
Let the degree measurement of the angles be represented by a−2d,a−d,a,a+d,a+2da-2 d, a-d, a, a+d, a+2 da−2d,a−d,a,a+d,a+2d. Then 5a=540∘5 \mathrm{a}=540^{\circ}5a=540∘ and a=108∘\mathrm{a}=108^{\circ}a=108∘.